Non-termination of sickness behavior as precipitating factor for mental disorders.

Sickness behavior can be defined as a combination of coordinated behavioral and physiological changes that develop in response to any condition that elicits pro-inflammatory activity. It is an adaptational homeostasis initiated by the influence of pro-inflammatory cytokines on central nervous system neurohormonal functioning. This paper introduces the concept of non-termination of sickness behavior as a potential threat to mental health. In view of the similarities between the behavioral symptoms, the neuroendocrine and the cytokine profiles of sickness behavior and that of a number of mental disorders it is hypothesized that the inappropriate continuation of sickness behavior, (i.e., non-termination), after recovery from the initial disease, could form the basis for mental disturbances. This would be particularly relevant in individuals with alterations in stress vulnerability (altered activation threshold and impaired negative feedback), which may occur due to the combination of genetic disposition and priming by early life experiences.